Grinding mill



Oct. 17, 1944. w. B. MARSHALL GRINDING MILL Filed April 25, 1941 2Sheets-Sheet 1 William B. Marshall INVENTOR. F $4 521444.

Oct. 17, 1944. w. a. MARSHALL GRINDING MILL Filed April 25, 1941 2Sheets-Sheet. 2

William B. Mars/m2! ATTORNEY.

Patented Oct. 17, 1944 GRINDING MILL William B. Marshall,

to Chain Belt Com Milwaukee, Wis., assignor P Milwaukee, Wis., a

corporation of Wisconsin Application April 25, 1941, Serial No. 390,253

3 Claims.

This invention relates to apparatus for grinding and is primarilyintended for fine grinding as in various industrial processingoperations.

The general object of theinvention is to provide novel apparatus forrapid and continuous grinding whereby a uniformly ground product may beobtained with a minimum of dust or undersized particles, all at loweredcost in time and power expenditure, and with maintenance of quiet andbalanced operation at all speeds.

According to one aspect of the invention, the.

grinding is accomplished by crowding particles against a smooth surfaceprovided with perforations located at close and contiguous spots, saidparticles penetrating said perforations, and while so penetrating, beingsheared by the action of the cutting members. In order to accomplishfine grinding, extremely close adjustment must be made between thecutting edges and the perforated surface, the provision for whichconstitutes a further object of this invention.

While I am. aware that screens and other perforai'e means have. beenemployed to restrain the passages of material through rotary mills untilthe material .5 reduced to the desired size, such screens have not beenused, as far as I am aware, to cooperate with the cutting means to shearthe material as herein disclosed.

The use of foraminous cages with hammer mills is not analogous in thatthe blades or beaters there employed pulverize the material by beatingit against either breaker plates or perforated sur-- faces. This resultsin the formation of dust and lack of uniformity in the ground materialwhich, in some of the uses here contemplated, makes the resultingproduct quite unsatisfactory.

The grinding action provided by this invention is further distinguishedby the fact that the blades operate in very close contact with a smoothsurface which is broken only by the perforated discharge passages. Thereare no grooves for shred ding the material or raised, breaker teeth forcrushing. Instead, the action includes a crowding eifect caused by therotor body which occupies nearly all the space within the casing,followed by the shaving of particle which are crowded into' theperforations. The remarkable feature of the invention is that the sizeof grind-. ings appear to have little, if any relation to the size ofthe perforations, said grindings being uniformly fine and very muchsmaller forations.

With the above and other objects in view which will be more apparent asthe description proceeds, the invention resides in the novelarrangements than the perof elements more fully described herein andparticularly pointed out in the appended claims.

Referring to the drawings, wherein like parts will be designated by likecharacters throughout:

Figure 1 is a vertical sectional view through the grinder on the line |lof Fig. 2; and

Figure 2 is a transverse sectional view through the grinder on the line2-2 of Fig. 1, the upper portion'of the rotor being shown in elevation.

The rotor I0 is made up of a number of cylindrical discs l'l splined toa shaft l 2, driven by any suitable source of power. For convenience inassembly and disassembly, a coupling l3may be secured to the end ofshaft H for cooperation with a mating coupling secured to the-powerinput shaft (not shown), a flywheel Hl being mounted on the rotor shaftin.this instance for absorbing load fluctuations.

Each disc I I- has mounted therein ery a plurality of angularly spacedand axially disposed cutter blades l5, which are the same width as thediscs in which they are mounted. Blades l5 are held securely in therotor discs I I by means of wedge blocks l6, which in turn are retainedby cap screws I! threaded into the respective discs. Ahead of each bladeis a flat portion I8 formed on the rotor disc, providing a pocket foraccumulation of material, which is pushed aheadby the cutter bladefollowing in its path. The blades IS on respective discs are staggeredso as to arrange the foremost blade in the center of the rotor, withblades in adjacent discs set back in general inverted V shape. There arepreferably provided a plurality of such rows, forming blade surfaces inherringbone fashion, the disposition of which promotes the spreading ofmaterial axially of the rotor over all parts of the cutting surface.

Rotor I0 is contained in a housing H! which is open at the top forreceiving materials. The feed inlet thus provided extends for somedistance above the highest point of the rotor in order that a column ofmaterial may be maintained for uniformity in feeding and the inletextends axially a distance equal to the sum of the widths of the rotordiscs ll. Preferably the feed inlet is disposed over' only approximatelyone quadrant of the rotor, the other upper quadrant being enclosed by anarcuate plate 20 provided with serrations 2l. Plate 20 serves thepurpose of directing material revolving with the rotor (direction ofrotation indicated by the arrow in Figure 1) back into the feed inlet,while the serrations afford a breaker surface for any material whichmight have revolved with the rotor through the at its periph- 'by struts40 connecting grinding zone without having been crowded into theperforations.

Housing 19 also extends somewhat below the rotor ID, the lowerextremities being flanged outwardly as at 22 to provide a base. Disposedwithin the housing and on the underside of rotor I is a grate frame 23with an approximately semicylindrical saddle 24 for supporting a gratemember 25 which rests thereon. Grate 25 is concentric with rotor and isslightly spaced therefrom. It forms an approximately continuous surfacewith the left wall 26 of the feed inlet and with the breaker plate whichare disposed above the rotor axis and form a part of the outer housingl9. It should be noted that the inner edges of the horizontal top plate21 of the grate frame 23 extend over the saddle 24 a short distance toform a ledge 28 at each end of the saddle. Each ledge is equal to thewidth of the grate and the shear plate 29 which is nested into the grateand securely attached thereto. Shear plate 29 and grate 25 need not bewelded or riveted to frame 23 but when slid into the saddle and underthe ledges 28 are held firmly in place.

Grate frame 23 is adjustably supported on housing H) by verticallydisposed bolts 30 which extend through plate 21 and are hung from ledges3| formed on the inside of housing l9. Horizontal adjustment may be madeby set screws 32 threaded through the sides of housing I9, advancing ofscrews on one side, of course, requiring the retracting of screws on theopposing side. To permit this horizontal adjustment, holes for bolts 30are slightly enlarged. The grate saddle is secured in adjusted positionby cap screws 33 which extendthrough enlarged holes in the end walls ofthe saddle frame and are threaded into housing l9, Accessibility tobolts 30 and screws 33 is provided by apertures 34 and 35 respectivelyin the side walls of housing I9, which apertures are normally covered byplates 36 retained by thumb screws 31 threaded into the sides of thehousing.

Grate 25 is supported intermediate the ends of the adjustable grateframe 23 by vertical, arcuate shaped plates 38 connected to each otherand to the end walls of the grate frame by central, vertical webs 39,thus completing the cradle 24. Still further stiffening of the frame 23is afforded the lower outer extremities of the end plates of the gratesupport.

From the foregoing description, it will be understood that the grateframe may be removed vertically from beneath the rotor and rotor housingby merely removing bolts 30 and screws 33 and releasing screws 32. Whenthe frame is so removed, the shear plate and backing grate may be slidout horizontally from nesting engagement with the grate frame 23 andeither replaced or turned end for end to promote more even wear acrossits entire exposed surface. When assembled beneath the rotor, the gratesaddle may be adjusted either vertically with respect,to the rotor bybolts 30, or it may be adjusted horizontally and transversely withregard to the rotor axis by set screws 32 and locked in position by capscrews 33. v

For supporting the rotor in the housing, suitable bearings must beprovided in the end sides of the housing, and the rotor should becapable of removal from the housing with a minimum of trouble. In Figure2 there is disclosed a bearing housing 41 which is bolted to one face ofthe housing l9 and is provided with an anti-friction bearing having aninner race 42 which is retained housing has bolted to for rotation withshaft l2 by collar 43. Race 42 abuts against a shoulder 44 on shaft l2and suitable sealing means 45 may be employed between shoulder 44 andhousing 4|. The end of shaft I2 is enclosed by a cap 46 which may befastened over the end of bearing housing 4 I.

To the opposite end of the housing [9 a removable, flanged cover 41 isbolted, Closing an aperture in the wall of the housing. The aperture islarger in diameter than that of the cutting rotor to permit its endwiseassembly and removal. The it, a bearing housing 48 in which isjournalled shaft l2. Bearing housing 43 and its bearing assembly areidentical to bearing housing 4| and its bearing assembly at the oppositeend .of the shaft. All members mounted on shaft l2 within the housingare clamped together by nut 49 and lock nut 50 threaded on shaft l2outside the open end bearing housing 48, said nuts cooperating withshoulder 44 on the opposite end of the shaft to maintain assembledrelation of said members. A look washer 5| may be interposed between thenuts to further prevent their accidental unscrewing.

At each end of the assembly of rotor discs H is a sealing plate 52preferably of slightly larger diameter than that of the discs, and alsosplined to shaft l2, which plates 52 are received in circular recessesformed respectively in the end wall of housing 19 and the cover 41. Withthis construction, when cap 46 and collar 43 are removed, it is onlynecessary to remove flanged cover 41 to withdraw the entire rotor fromthe housing. Of course, to remove the discs from shaft l2, the bearingassembly of the housing 48 must be removed prior to sliding the discsoff the shaft.

The machine having been described in deta l, the operation may now besummarized, as well as the method which is carried out thereby.

The rotor is designed to operate at high speeds, which may be of theorder of 1750 R. P. M. and when so rotated it drags material with itfrom the feed inlet to the enclosed lower portion where the perforatedshear plate 29 is disposed. It is difficult to give exact dimensions ofshear plate openings because they vary for optimum results withdifferent materials.

In grinding soft, whole kernel corn, oval perforations axially of therotor by circumferentially appeared to give desirable results. In thisinstance the shear plate was about /8" thick and the perforations werespaced as closely together as the strength of the material would safelypermit. The perforations in the supporting grate 25 were many timeslarger in order to afford as little restriction as possible to thepassage of material through shear plate 29, consistent withstrengthening requirements. With the shear plate closely adjusted forsmall clearance with the rotating blades, and with the aperturesmentioned, it was possible to shear the skins of the kernels, so theywould ultimately p ss through the perforations along with the rest ofthe material, a result which could not be satisfactorily obtained withother machines heretofore employed.

In grinding dry fish scrap, it was found that round apertures in theshear plate of approximately A diameter, and with centers staggered andspaced approximately :5" apart, gave good results, the material, whichincluded bones, being ground to a uniform fine powder withoutappreciable dust.

These results are given by means of illustration and are not intended aslimitations of the scope of the invention. They indicate the necessityof experimentation with different materials and adjustment necessary togive optimum results.

For continuous operation a column of material should be maintained inthe feed inlet above the rotor. With each passage of the rotor a layerwill be swept off the bottom of this column and due to the spaceoccupancy of the rotor, will be spread out and crowded against thecutting surface. This surface is entirely smooth except for theperforations before described, yet this is apparently suflicient toretard the movement of materials and enable the blades to perform theirshearing or shaving function. Should material revolve with the rotorpast the shear plate, it is directed back into the feed by plate 20,which plate is preferably serrated to break up any larger pieces in thematerial being ground.

The provision of the pocket I 8 ahead of the cutter is considered afactor in securing improved results, as is the herringbone dispositionof the cutting members, the latter facilitating the spreading ofmaterial axially of the rotor and into the cutting perforations.

Since different processes and/or materials may require'difference in thefineness of the grinding, it is highly desirable that the shear iplatebe replaceable so that the same machine may be utilized for differentoperations. The present invention is believed to afford an eificient andconvenient manner of accomplishing this.

What I claim is:

1. In a rotary grinder having an internal casing which is generallycylindrical in shape with contour having apertures therein for dischargeof ground material, a, rotor comprising a plurality of disc membersmounted side by side and arranged to rotate within said casing, andcutting tially spaced in herringbone fashion, whereby material may bespread laterally across the lower surface of the casing and sheared bythe cutting members before passing through said apertures.

2. A rotary grinder comprising a casing with an opening in its upperportion for receiving material and a grinding cage enclosing its lowerportion, said grinding cage consisting of a smooth curved surface havingapertures therein for discharge of ground material, a rotor mounted insaid casing occupying substantially the entire volume thereof andadapted upon rotation to crowd material against said surface, said.roto'r,

comprising a plurality of disc members mounted side by side, each discmember having a cutting edge in its periphery extending forsubstantially the full width of the disc, the cutting edges in adjacentdiscs being circumferentially. spaced, each cutting edge making shearingcontact with the edges of the apertures in said surface and the portionsof the discs ahead of the cutting edges being depressed below theperipheral surface of an adjacent disc whereby material which is notdischarged through perforations in the path of one of said cutting edgesmay be laterally moved into the depressed portion ahead of an adjacentcutting edge.

3. In a rotary grinder comprising a casing which is generallycylindrical in shape with an opening in its upper portion for receivingmaterial and a lower surface of smooth curved contour having aperturestherein for discharge of ground material, a rotor mounted in said casingof substantially cylindrical contour having cutting edges disposed onits periphery, each cutting edge extending generally longitudinally ofthe rotor and in close cutting proximity for the full length of theedge'to the curved lower surface of the casing when rotated injuxtaposed position thereto, each said edge extending for only a portionof the length of said rotor, and iongitudinally adjacent edges beingspaced circumferentially in staggered relationship and rotating insubstantially contiguous paths.

' WILLIAM B. MARSHALL.

